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DISTINCT predicate

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

Some databases support the DISTINCT predicate, which serves as a convenient, NULL-safe comparison predicate. With the DISTINCT predicate, the following truth table can be assumed:

  • [ANY] IS DISTINCT FROM NULL yields TRUE
  • [ANY] IS NOT DISTINCT FROM NULL yields FALSE
  • NULL IS DISTINCT FROM NULL yields FALSE
  • NULL IS NOT DISTINCT FROM NULL yields TRUE

For instance, you can compare two fields for distinctness, ignoring the fact that any of the two could be NULL, which would lead to funny results. This is supported by jOOQ as such: 

TITLE IS DISTINCT FROM SUB_TITLE
TITLE IS NOT DISTINCT FROM SUB_TITLE
BOOK.TITLE.isDistinctFrom(BOOK.SUB_TITLE)
BOOK.TITLE.isNotDistinctFrom(BOOK.SUB_TITLE)

Dialect support

This example using jOOQ:

AUTHOR.FIRST_NAME.isDistinctFrom(AUTHOR.LAST_NAME)

Translates to the following dialect specific expressions:

ASE, Exasol, SQLDataWarehouse, Vertica

NOT EXISTS (
  SELECT AUTHOR.FIRST_NAME x
  INTERSECT
  SELECT AUTHOR.LAST_NAME x
)

Aurora MySQL, MariaDB, MemSQL, MySQL

(NOT(AUTHOR.FIRST_NAME <=> AUTHOR.LAST_NAME))

Aurora Postgres, BigQuery, CockroachDB, DB2, DuckDB, Firebird, H2, HSQLDB, Postgres, Redshift, SQLServer, Snowflake, Trino, YugabyteDB

AUTHOR.FIRST_NAME IS DISTINCT FROM AUTHOR.LAST_NAME

ClickHouse

arrayUniq(ARRAY(AUTHOR.FIRST_NAME, AUTHOR.LAST_NAME)) = 2

Derby

NOT EXISTS (
  SELECT AUTHOR.FIRST_NAME x
  FROM SYSIBM.SYSDUMMY1
  INTERSECT
  SELECT AUTHOR.LAST_NAME x
  FROM SYSIBM.SYSDUMMY1
)

Hana, Sybase

NOT EXISTS (
  SELECT AUTHOR.FIRST_NAME x
  FROM SYS.DUMMY
  INTERSECT
  SELECT AUTHOR.LAST_NAME x
  FROM SYS.DUMMY
)

Informix

NOT EXISTS (
  SELECT AUTHOR.FIRST_NAME x
  FROM (
    SELECT 1 AS dual
    FROM systables
    WHERE (tabid = 1)
  ) AS dual
  INTERSECT
  SELECT AUTHOR.LAST_NAME x
  FROM (
    SELECT 1 AS dual
    FROM systables
    WHERE (tabid = 1)
  ) AS dual
)

Oracle

decode(AUTHOR.FIRST_NAME, AUTHOR.LAST_NAME, 1, 0) = 0

SQLite

(AUTHOR.FIRST_NAME IS NOT AUTHOR.LAST_NAME)

Teradata

NOT EXISTS (
  SELECT AUTHOR.FIRST_NAME x
  FROM (
    SELECT 1 AS "dual"
  ) AS "dual"
  INTERSECT
  SELECT AUTHOR.LAST_NAME x
  FROM (
    SELECT 1 AS "dual"
  ) AS "dual"
)

Access

/* UNSUPPORTED */
Generated with jOOQ 3.20. Translate your own SQL on our website

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